* [PATCH] memfd: Check for non-NULL file_seals in memfd_create() syscall
@ 2023-06-07 13:24 Roberto Sassu
2023-06-07 17:21 ` Andrew Morton
0 siblings, 1 reply; 4+ messages in thread
From: Roberto Sassu @ 2023-06-07 13:24 UTC (permalink / raw)
To: akpm; +Cc: linux-kernel, Roberto Sassu, stable
From: Roberto Sassu <roberto.sassu@huawei.com>
Ensure that file_seals is non-NULL before using it in the memfd_create()
syscall. One situation in which memfd_file_seals_ptr() could return a NULL
pointer is when CONFIG_SHMEM=n.
Cc: stable@vger.kernel.org # 4.16.x
Fixes: 47b9012ecdc7 ("shmem: add sealing support to hugetlb-backed memfd")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
mm/memfd.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/memfd.c b/mm/memfd.c
index 69b90c31d38..e763e76f110 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -371,12 +371,15 @@ SYSCALL_DEFINE2(memfd_create,
inode->i_mode &= ~0111;
file_seals = memfd_file_seals_ptr(file);
- *file_seals &= ~F_SEAL_SEAL;
- *file_seals |= F_SEAL_EXEC;
+ if (file_seals) {
+ *file_seals &= ~F_SEAL_SEAL;
+ *file_seals |= F_SEAL_EXEC;
+ }
} else if (flags & MFD_ALLOW_SEALING) {
/* MFD_EXEC and MFD_ALLOW_SEALING are set */
file_seals = memfd_file_seals_ptr(file);
- *file_seals &= ~F_SEAL_SEAL;
+ if (file_seals)
+ *file_seals &= ~F_SEAL_SEAL;
}
fd_install(fd, file);
--
2.25.1
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] memfd: Check for non-NULL file_seals in memfd_create() syscall
2023-06-07 13:24 [PATCH] memfd: Check for non-NULL file_seals in memfd_create() syscall Roberto Sassu
@ 2023-06-07 17:21 ` Andrew Morton
2023-06-08 21:05 ` Roberto Sassu
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Morton @ 2023-06-07 17:21 UTC (permalink / raw)
To: Roberto Sassu
Cc: linux-kernel, Roberto Sassu, stable, Marc-André Lureau,
Mike Kravetz
On Wed, 7 Jun 2023 15:24:27 +0200 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Ensure that file_seals is non-NULL before using it in the memfd_create()
> syscall. One situation in which memfd_file_seals_ptr() could return a NULL
> pointer is when CONFIG_SHMEM=n.
Thanks. Has thie crash actually been demonstrated?
> --- a/mm/memfd.c
> +++ b/mm/memfd.c
> @@ -371,12 +371,15 @@ SYSCALL_DEFINE2(memfd_create,
>
> inode->i_mode &= ~0111;
> file_seals = memfd_file_seals_ptr(file);
> - *file_seals &= ~F_SEAL_SEAL;
> - *file_seals |= F_SEAL_EXEC;
> + if (file_seals) {
> + *file_seals &= ~F_SEAL_SEAL;
> + *file_seals |= F_SEAL_EXEC;
> + }
> } else if (flags & MFD_ALLOW_SEALING) {
> /* MFD_EXEC and MFD_ALLOW_SEALING are set */
> file_seals = memfd_file_seals_ptr(file);
> - *file_seals &= ~F_SEAL_SEAL;
> + if (file_seals)
> + *file_seals &= ~F_SEAL_SEAL;
> }
>
> fd_install(fd, file);
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] memfd: Check for non-NULL file_seals in memfd_create() syscall
2023-06-07 17:21 ` Andrew Morton
@ 2023-06-08 21:05 ` Roberto Sassu
2023-06-08 21:29 ` Roberto Sassu
0 siblings, 1 reply; 4+ messages in thread
From: Roberto Sassu @ 2023-06-08 21:05 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-kernel, Roberto Sassu, stable, Marc-André Lureau,
Mike Kravetz
On 6/7/2023 7:21 PM, Andrew Morton wrote:
> On Wed, 7 Jun 2023 15:24:27 +0200 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
>
>> From: Roberto Sassu <roberto.sassu@huawei.com>
>>
>> Ensure that file_seals is non-NULL before using it in the memfd_create()
>> syscall. One situation in which memfd_file_seals_ptr() could return a NULL
>> pointer is when CONFIG_SHMEM=n.
>
> Thanks. Has thie crash actually been demonstrated?
Welcome. Yes, I noticed it when booting Fedora 38:
Jun 07 11:45:17 localhost kernel: BUG: kernel NULL pointer dereference, address: 0000000000000000
Jun 07 11:45:17 localhost kernel: #PF: supervisor write access in kernel mode
Jun 07 11:45:17 localhost kernel: #PF: error_code(0x0002) - not-present page
Jun 07 11:45:17 localhost kernel: PGD 0 P4D 0
Jun 07 11:45:17 localhost kernel: Oops: 0002 [#1] PREEMPT SMP NOPTI
Jun 07 11:45:17 localhost kernel: CPU: 0 PID: 752 Comm: dbus-broker-lau Not tainted 6.4.0-rc1+ #596
Jun 07 11:45:17 localhost kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Jun 07 11:45:17 localhost kernel: RIP: 0010:__do_sys_memfd_create+0x2a4/0x320
Jun 07 11:45:17 localhost kernel: Code: ff 83 e3 02 0f 84 6a ff ff ff 49 81 7d 28 00 cd 24 82 74 0c 4c 89 ef e8 5a 6c 27 00 84 c0 74 29 49 8b 45 20 48 05 88 04 00 0>
Jun 07 11:45:17 localhost kernel: RSP: 0018:ffffc900007d3ef8 EFLAGS: 00010246
Jun 07 11:45:17 localhost kernel: RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000
Jun 07 11:45:17 localhost kernel: RDX: 0000000000000003 RSI: 0000000000000004 RDI: ffff888012ab1600
Jun 07 11:45:17 localhost kernel: RBP: ffff888025eb4d60 R08: 0000000000000000 R09: 0000000000000000
Jun 07 11:45:17 localhost kernel: R10: ffffffff83524c90 R11: 0000000000000000 R12: 000000000000000c
Jun 07 11:45:17 localhost kernel: R13: ffff888012ab1600 R14: ffff888025eb4d66 R15: 0000000000000000
Jun 07 11:45:17 localhost kernel: FS: 00007f4ef466de80(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000
Jun 07 11:45:17 localhost kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Jun 07 11:45:17 localhost kernel: CR2: 0000000000000000 CR3: 000000000e7fe000 CR4: 0000000000350ef0
Jun 07 11:45:17 localhost kernel: Call Trace:
Jun 07 11:45:17 localhost kernel: <TASK>
Jun 07 11:45:17 localhost kernel: do_syscall_64+0x3b/0x90
Jun 07 11:45:17 localhost kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
Jun 07 11:45:17 localhost kernel: RIP: 0033:0x7f4ef4a0dd2d
Jun 07 11:45:17 localhost kernel: Code: c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 0>
Jun 07 11:45:17 localhost kernel: RSP: 002b:00007fff308c5b58 EFLAGS: 00000246 ORIG_RAX: 000000000000013f
Jun 07 11:45:17 localhost kernel: RAX: ffffffffffffffda RBX: 00005597c14742d8 RCX: 00007f4ef4a0dd2d
Jun 07 11:45:17 localhost kernel: RDX: 00007f4ef49dfa5b RSI: 0000000000000003 RDI: 00005597c0b8f778
Jun 07 11:45:17 localhost kernel: RBP: 00007fff308c5b80 R08: 0000000000000000 R09: 00007fff308c5fa0
Jun 07 11:45:17 localhost kernel: R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
Jun 07 11:45:17 localhost kernel: R13: 00007fff308c5e60 R14: 00007fff308c5c20 R15: 00007fff308c5c00
Jun 07 11:45:17 localhost kernel: </TASK>
Jun 07 11:45:17 localhost kernel: Modules linked in: sunrpc intel_rapl_msr intel_rapl_common kvm_amd snd_hda_codec_generic ccp snd_hda_intel snd_intel_dspcfg iTCO_w>
Jun 07 11:45:17 localhost kernel: CR2: 0000000000000000
Jun 07 11:45:17 localhost kernel: ---[ end trace 0000000000000000 ]---
Thanks for picking the patches. If it is still possible, it seems
that the Fixes tag is incorrect. The fixed commit should be:
c3b1b1cbf002 ("ramfs: add support for "mode=" mount option")
Roberto
>> --- a/mm/memfd.c
>> +++ b/mm/memfd.c
>> @@ -371,12 +371,15 @@ SYSCALL_DEFINE2(memfd_create,
>>
>> inode->i_mode &= ~0111;
>> file_seals = memfd_file_seals_ptr(file);
>> - *file_seals &= ~F_SEAL_SEAL;
>> - *file_seals |= F_SEAL_EXEC;
>> + if (file_seals) {
>> + *file_seals &= ~F_SEAL_SEAL;
>> + *file_seals |= F_SEAL_EXEC;
>> + }
>> } else if (flags & MFD_ALLOW_SEALING) {
>> /* MFD_EXEC and MFD_ALLOW_SEALING are set */
>> file_seals = memfd_file_seals_ptr(file);
>> - *file_seals &= ~F_SEAL_SEAL;
>> + if (file_seals)
>> + *file_seals &= ~F_SEAL_SEAL;
>> }
>>
>> fd_install(fd, file);
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] memfd: Check for non-NULL file_seals in memfd_create() syscall
2023-06-08 21:05 ` Roberto Sassu
@ 2023-06-08 21:29 ` Roberto Sassu
0 siblings, 0 replies; 4+ messages in thread
From: Roberto Sassu @ 2023-06-08 21:29 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-kernel, Roberto Sassu, stable, Marc-André Lureau,
Mike Kravetz
On 6/8/2023 11:05 PM, Roberto Sassu wrote:
> On 6/7/2023 7:21 PM, Andrew Morton wrote:
>> On Wed, 7 Jun 2023 15:24:27 +0200 Roberto Sassu
>> <roberto.sassu@huaweicloud.com> wrote:
>>
>>> From: Roberto Sassu <roberto.sassu@huawei.com>
>>>
>>> Ensure that file_seals is non-NULL before using it in the memfd_create()
>>> syscall. One situation in which memfd_file_seals_ptr() could return a
>>> NULL
>>> pointer is when CONFIG_SHMEM=n.
>>
>> Thanks. Has thie crash actually been demonstrated?
>
> Welcome. Yes, I noticed it when booting Fedora 38:
>
> Jun 07 11:45:17 localhost kernel: BUG: kernel NULL pointer dereference,
> address: 0000000000000000
> Jun 07 11:45:17 localhost kernel: #PF: supervisor write access in kernel
> mode
> Jun 07 11:45:17 localhost kernel: #PF: error_code(0x0002) - not-present
> page
> Jun 07 11:45:17 localhost kernel: PGD 0 P4D 0
> Jun 07 11:45:17 localhost kernel: Oops: 0002 [#1] PREEMPT SMP NOPTI
> Jun 07 11:45:17 localhost kernel: CPU: 0 PID: 752 Comm: dbus-broker-lau
> Not tainted 6.4.0-rc1+ #596
> Jun 07 11:45:17 localhost kernel: Hardware name: QEMU Standard PC (Q35 +
> ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
> Jun 07 11:45:17 localhost kernel: RIP:
> 0010:__do_sys_memfd_create+0x2a4/0x320
> Jun 07 11:45:17 localhost kernel: Code: ff 83 e3 02 0f 84 6a ff ff ff 49
> 81 7d 28 00 cd 24 82 74 0c 4c 89 ef e8 5a 6c 27 00 84 c0 74 29 49 8b 45
> 20 48 05 88 04 00 0>
> Jun 07 11:45:17 localhost kernel: RSP: 0018:ffffc900007d3ef8 EFLAGS:
> 00010246
> Jun 07 11:45:17 localhost kernel: RAX: 0000000000000000 RBX:
> 0000000000000002 RCX: 0000000000000000
> Jun 07 11:45:17 localhost kernel: RDX: 0000000000000003 RSI:
> 0000000000000004 RDI: ffff888012ab1600
> Jun 07 11:45:17 localhost kernel: RBP: ffff888025eb4d60 R08:
> 0000000000000000 R09: 0000000000000000
> Jun 07 11:45:17 localhost kernel: R10: ffffffff83524c90 R11:
> 0000000000000000 R12: 000000000000000c
> Jun 07 11:45:17 localhost kernel: R13: ffff888012ab1600 R14:
> ffff888025eb4d66 R15: 0000000000000000
> Jun 07 11:45:17 localhost kernel: FS: 00007f4ef466de80(0000)
> GS:ffff88807dc00000(0000) knlGS:0000000000000000
> Jun 07 11:45:17 localhost kernel: CS: 0010 DS: 0000 ES: 0000 CR0:
> 0000000080050033
> Jun 07 11:45:17 localhost kernel: CR2: 0000000000000000 CR3:
> 000000000e7fe000 CR4: 0000000000350ef0
> Jun 07 11:45:17 localhost kernel: Call Trace:
> Jun 07 11:45:17 localhost kernel: <TASK>
> Jun 07 11:45:17 localhost kernel: do_syscall_64+0x3b/0x90
> Jun 07 11:45:17 localhost kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
> Jun 07 11:45:17 localhost kernel: RIP: 0033:0x7f4ef4a0dd2d
> Jun 07 11:45:17 localhost kernel: Code: c3 66 2e 0f 1f 84 00 00 00 00 00
> 66 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8
> 4c 8b 4c 24 08 0f 0>
> Jun 07 11:45:17 localhost kernel: RSP: 002b:00007fff308c5b58 EFLAGS:
> 00000246 ORIG_RAX: 000000000000013f
> Jun 07 11:45:17 localhost kernel: RAX: ffffffffffffffda RBX:
> 00005597c14742d8 RCX: 00007f4ef4a0dd2d
> Jun 07 11:45:17 localhost kernel: RDX: 00007f4ef49dfa5b RSI:
> 0000000000000003 RDI: 00005597c0b8f778
> Jun 07 11:45:17 localhost kernel: RBP: 00007fff308c5b80 R08:
> 0000000000000000 R09: 00007fff308c5fa0
> Jun 07 11:45:17 localhost kernel: R10: 0000000000000000 R11:
> 0000000000000246 R12: 0000000000000000
> Jun 07 11:45:17 localhost kernel: R13: 00007fff308c5e60 R14:
> 00007fff308c5c20 R15: 00007fff308c5c00
> Jun 07 11:45:17 localhost kernel: </TASK>
> Jun 07 11:45:17 localhost kernel: Modules linked in: sunrpc
> intel_rapl_msr intel_rapl_common kvm_amd snd_hda_codec_generic ccp
> snd_hda_intel snd_intel_dspcfg iTCO_w>
> Jun 07 11:45:17 localhost kernel: CR2: 0000000000000000
> Jun 07 11:45:17 localhost kernel: ---[ end trace 0000000000000000 ]---
>
> Thanks for picking the patches. If it is still possible, it seems
> that the Fixes tag is incorrect. The fixed commit should be:
>
> c3b1b1cbf002 ("ramfs: add support for "mode=" mount option")
Ops, sorry. The comment above was for the patch: shmem: Use
ramfs_kill_sb() for kill_sb method of ramfs-based tmpfs.
Thanks
Roberto
> Roberto
>
>>> --- a/mm/memfd.c
>>> +++ b/mm/memfd.c
>>> @@ -371,12 +371,15 @@ SYSCALL_DEFINE2(memfd_create,
>>> inode->i_mode &= ~0111;
>>> file_seals = memfd_file_seals_ptr(file);
>>> - *file_seals &= ~F_SEAL_SEAL;
>>> - *file_seals |= F_SEAL_EXEC;
>>> + if (file_seals) {
>>> + *file_seals &= ~F_SEAL_SEAL;
>>> + *file_seals |= F_SEAL_EXEC;
>>> + }
>>> } else if (flags & MFD_ALLOW_SEALING) {
>>> /* MFD_EXEC and MFD_ALLOW_SEALING are set */
>>> file_seals = memfd_file_seals_ptr(file);
>>> - *file_seals &= ~F_SEAL_SEAL;
>>> + if (file_seals)
>>> + *file_seals &= ~F_SEAL_SEAL;
>>> }
>>> fd_install(fd, file);
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2023-06-08 21:29 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-06-07 13:24 [PATCH] memfd: Check for non-NULL file_seals in memfd_create() syscall Roberto Sassu
2023-06-07 17:21 ` Andrew Morton
2023-06-08 21:05 ` Roberto Sassu
2023-06-08 21:29 ` Roberto Sassu
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®